1. Field of Invention
The present invention relates to valve stem seal assemblies of the type installed over valve stems reciprocally movable within valve guides of internal combustion engines, and more particularly to seal assembly retainers incorporating specially designed retention fingers for securement of such assemblies to the valve guides.
2. Description of the Prior Art
Those skilled in the art will appreciate the manner in which intake and exhaust valves are employed in cylinder heads of internal combustion engines. Such valves, supported for reciprocal motion within valve guides, typically include integral elongated stems extending away from the engine cylinder heads, the ends of the stems interacting with rotating overhead cams for cyclic or repeated opening and closure of the valves against the force of valve return springs during the combustion cycle. Obviously, in order to permit unobstructed reciprocal movement of the stem in the guide, some mechanical clearance must exist between the valve guide and the moving stem. A plurality of valve stems thus move reciprocally to and from the cylinder head, each within its individual guide, and so-called valve stem seal assemblies are used to seal against leakage of oil through a mechanical clearance path between each annular engine valve guide and its associated valve stem.
As is well known, the intake port of a combustion chamber is opened and closed by the reciprocating motion of at least one intake valve, which in turn is driven by the rotary motion of a cam, the latter being affixed to and rotatable with an engine camshaft. The intake valve permits fuel mixed with air to flow into the combustion chamber. In addition, an internal combustion engine has at least one exhaust valve and associated exhaust port for releasing expended combustion gases to the atmosphere. Typically, intake and exhaust valves are of similar construction, and both include stems integrally affixed to the valves.
In the typical engine, a valve stem seal assembly is fitted over or atop each valve guide, wherein each seal assembly includes a retainer frictionally mounted to an associated valve guide. Each valve stem seal assembly normally has two primary parts: 1) an elastomeric oil seal for controlling leakage of oil between the valve stem and guide as noted, and 2) a structural cylindrical retainer mounted atop of the valve guide to hold the oil seal in place.
While much progress has been achieved in valve stem seal design, performance, and construction, the installation and securement of valve seal assemblies remain areas in need of improvement. For example, in an original equipment assembly environment, there is need for improvement in feedback with respect to depth of insertion of the valve guide retainer onto the valve guide to assure proper installation. Many such retainers rely only on sliding friction for securement to valve guides. Others rely on barbs within the interior of the retainer to develop sufficient friction force for assuring adequate securement. Indicia, such as an audible click upon proper insertion, would be welcomed. In addition, a more secure mechanical retention of the assembly in the typically vibrating engine environment would be welcomed.
The valve stem seal retainer of the present invention addresses installation issues, and incorporates a positive mechanical coupling mechanism to assure proper retention of the valve stem seal assembly to valve guides.
The disclosed invention is a two-piece valve stem seal and retainer assembly for an internal combustion engine. A plurality of such assemblies is contemplated for use in an engine, each designed for insertion over an engine valve guide for continuous engagement with an associated reciprocally moveable valve stem. The elastomer seal body includes a circumferential aperture containing at least one radially inwardly directed sealing lip adapted to engage the stem to minimize the escape of oil lubricant from the engine, particularly along a path between the valve guide and the reciprocally moving valve stem seal.
In its preferred form, the seal body contains an annular groove adapted to receive an end wall in the upper extremity of the retainer. The retainer, formed of metal, comprises a cylindrical body containing a plurality of axially depending spring fingers. The bottom extremities of the fingers have inwardly turned ends adapted to mechanically engage a circumferentially disposed groove or step of a boss formed in the mating exterior cylindrical surface of an associated valve guide. In their preferred form, the fingers are provided in two alternate embodiments, each defining reverse bends for assuring resilient mechanical engagement with the valve guide. The first embodiment of the retainer, adapted to mechanically engage a circumferentially disposed groove in the guide, comprises a bowed cross-section at its lower guide-engaging end. Traversing downwardly along the retainer cross-section, each axially depending spring finger flares radially outwardly or away from the axially extending valve guide body, then bends radially inwardly toward the valve guide body, and finally reversibly upwardly, becoming parallel to the valve guide surface.
The second embodiment, adapted to engage a circumferentially disposed step of a boss on the guide, is without such a flare. Instead, at the bottom of its axial length, the cross-section of the second embodiment reverses its direction one hundred eighty degrees at its lowest extremity, thus becoming parallel to the body of the valve guide. The reverse bends of both embodiments impart a robust spring function to the mechanically engageable valve guide-connecting ends of the retainers. In each case, an audible click sound provides proof of proper securement upon installation. In addition, in both embodiments the connection mechanism is not only resilient, but also mechanically positive, and hence more reliable.